//Do not declare variable marks.
//Write your code below this line.
if(marks>90)
    { console.log("AA");}
else if(marks>80&&marks<=90)
    {console.log("AB");}
else if(marks>60&&marks<=70)
    { console.log("BB");}
else if(marks>50&&mrks<=60)
   {console.log("CC");}
else if(marks>40&&marks<=50)
    {console.log("CD");}
else if(marks>30&&marks<=40)
    {console.log("DD");}
else if(marks<=30)
    {console.log("FF");}